1. Field of the Invention
This invention relates to a composition for use as a direct compression tableting agent for a tablet containing interractive ingredients and the process for making the same. More particularly, this invention relates to a compressible coated iron composition which minimizes interaction with other active ingredients in the tablet. It is specifically suited for use in tablets containing vitamin C to minimize reaction between iron and vitamin C in the tablet formulations.
2. Description of the Prior Art
As a solid dosage form, the tablet is the most popular and useful form of oral medication for dispensing active ingredients such as pharmaceuticals, vitamins, and minerals. The compressed tablet offers several advantages over other solid dosage forms. These advantages include greater accuracy of dosage, more convenient administration, increased durability and stability during storage, shorter production time, and economy and efficiency in storage, packaging and shipping.
Tablets can be prepared using several established methods such as wet granulation, dry granulation, and direct compression. The most desirable method from the standpoint of the processing procedures, equipment and materials is the direct compression method. This method increases the efficiency of tableting operations and reduces costs by requiring the least amount of space and labor.
In a dry direct compression method, the ingredients are simply dry-mixed and then compressed. There is no granulation stage. It is essential that each component is uniformly dispersed within the mixture. Any tendency for component segregation must be minimized to assure that each tablet contains an accurate reproducible dosage. In addition, the mixture must have certain flow characteristics to allow accurate and convenient transport and must be cohesive when compressed. To reduce segregation tendencies the particle size distribution, shape, and density of all the ingredients should be similar. There are only a few substances available in forms which could be compressed directly without further treatment. If these ingredient characteristics are not present, then one of the granulation methods should probably be used.
There are also some limitations to the use of direct compression tableting. First, while compression of some components may produce tablets that do not disintegrate, other components of the tablet may interfere with the compressibility of the tablet composition and thus minimize the usefulness of this method. Second, most materials possess relatively weak intermolecular attraction thereby affecting the compacting of the ingredients into tablets. Third, with some formulations, the percentage of active ingredient is so small that direct compression would be impractical and uneconomical. However, in this case, an inert compressible diluent can be used to increase bulk in order to make the tablet a practical size for compression.
The direct compression method is a rather simple procedure compared to the more complicated and time consuming wet process method. Relatively inexpensive and unreactive chemicals are commonly used as the major component in direct compressible formulations. However, only a very limited number of materials possess the necessary cohesive strength and flowability to allow direct compression without requiring granulation. Modification is often required either by treating the material in some manner during the earlier stages of preparation or by adding a binder or excipient material which will surround or coat the active ingredient thereby forming an easily compressible excipient.
A tableting agent was sought which would protect the active ingredient from other tablet ingredients with which it may react and also have the desirable property of good granulation. The two essential characteristics required for such an agent are fluidity, which is necessary for the transport of the material through the hopper into the feed frame, and compressibility which is the property of forming a stable, compact mass when pressure is applied. Other desirable characteristics include rapid disintegration following ingestion, physiological inertness, capacity to bind poorly compressible ingredients and low cost.
Direct compressible diluents currently available as single entities include microcrystalline cellulose, dibasic calcium phosphate, lactose, spray dried lactose, mannitol and sorbitol. There are also blended vehicles containing all essential materials except the active ingredients.
One method of preparing direct compressible blended excipients is with a spray dryer. The process consists of wetting the powders to form granules, then drying the granules in the same equipment. A fluid bed dryer adapted to function as a wet granulator as well as a dryer is used for this purpose. Finely divided powder materials of a preselected formula are loaded into a container with a fine screen bottom. The container is inserted inside the dryer and thereafter a current of warm air blows upward through the screen mixing the powders. A granulating liquid consisting of a mixture of gums is introduced from above through a spray nozzle and is distributed among the powders by the turbulent air stream. Once all the fluid has been added, drying proceeds to the desired end point. The rate of addition of the liquid and the volume and temperature of the air is regulated such that granules form and remain airborne. The granules must be allowed to grow somewhat larger than desired size because during the drying step, these granules tend to abrade each other and become smaller. Milling of the desired product may be performed to breakdown any large particles.
This process produces granules that have suitable flow and blending properties for compression from powders which have poor tableting characteristics. Additionally, the process provides for control over granule particle size, even distribution of the granulating liquid and a means for precise control over the moisture level in the granulation process. Once this vehicle is prepared, other active ingredients may be added and compressed directly into tablets employing conventional techniques and apparatus.
The term "active ingredient" as used herein means any material intended for ingestion having a beneficial or desirable effect on the user.